Use of principal component analysis to evaluate thermal properties and combustibility of coffee-pine wood briquettes

C.L. Mendoza Martinez¹²³*, E. Sermyagina¹, M. Silva de Jesus³ and E. Vakkilainen¹

¹LUT University, School of Energy Systems, Yliopistonkatu 34, FI-53850 Lappeenranta, Finland
²Federal University of minas Gerais, Department of Chemical Engineering, Av. Antônio Carlos 6627, MG 31270-901 Belo Horizonte, Brazil
³Federal University of Viçosa, Department of Forest Engineering, Av. Peter Henry Rolfs, s/n - University Campus, MG 36570-900, Viçosa, Brazil
*Correspondence: clara.mendoza.martinez@lut.fi

Abstract:

The coffee production chain is a potential source of residual biomass inherent to the high productivity that can contribute to the generation of value-added products. The residues from the coffee sector are typically disposed to landfill without treatment causing potential environmental inconveniences. Briquetting presents an alternative process to produce a uniform fuel with high energy density. Briquettes facilitates easy transportation, enables better handling and storage of biomass residues. Properties such as low equilibrium moisture content, high energy density and compressive strength were reported for different coffee-pine wood briquettes treatments. Moreover, understanding of the thermal properties of the briquettes during combustion is crucial to evaluate their final application. This research is the first study that investigates the combustibility properties and kinetic parameters of the thermal decomposition of briquettes from coffee-pine wood using differential and integral thermal analysis under non-isothermal conditions. Multivariate analysis of the collected parameters through principal components analysis (PCA), was implemented to reduce the dimensionality of the data.
The desired profile in the combustibility is directly related to high temperatures and long burning times, thus, the tested briquettes displayed a significant combustibility potential, reporting peak temperatures and burnout times around 600 °C and 27 minutes, respectively. Activation energy kinetic parameter in the range of 12–42 kJ mol^-1 and average reactivity of 0.14–0.22 min^-1, were also found. The results revealed the not thermally hard material to degrade when compared to biomasses typically used for combustion.

Key words:

briquette, chemometrics, combustion rate, reactivity, solid biofuels

Utilization of waste biomass from post–harvest lines in the form of briquettes for energy production

A. Brunerová*, M. Brožek and M. Müller

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Material Science and anufacturing Technology, Kamýcká 129, CZ165 00 Prague, Czech Republic *Correspondence:brunerova@tf.czu.cz

Abstract:

A great amount of herbal waste biomass is produced nowadays during agriculture crop processing; also during ‘post–harvest lines’ operations. Such waste biomass occurs in the bulk form, thus, is not suitable for direct combustion; it can be improved by using of briquetting technology. Therefore, present paper provides chemical, mechanical and microscopic analyses of waste biomass originating from post–harvest lines and briquettes produced from it. Namely, waste biomass originated from production of oat (Avena sativa) – husks, wheat (Triticum spp.) – husks and poppy (Papaver somniferum) – straw and seed pods and mixture of all mentioned were investigated. Unprocessed materials were subjected to microscopic and chemical analysis and subsequently produced briquette samples were subjected to determination of its mechanical quality. A satisfactory level of moisture and ash content was observed, as well as, materials energy potential; oat – 17.39 MJ kg^-1, wheat – 17.04 MJ kg^-1, poppy – 14.48 MJ kg^-1. Also microscopic analysis proved suitability of all feedstock materials within evaluation of geometrical shapes of their particles. However, evaluation of briquette mechanical quality unsatisfactory results. Process of briquetting revealed unsuitability of oat feedstock for briquette production; other materials proved following values of volume density and mechanical durability (in sequence): wheat – 1,023.19 kg m^-3, 89.1%; poppy – 1,141.43 kg m^-3, 94.7%; mixture – 972.49 kg m^-3, 62.7%. In general, only poppy briquettes achieved requested mechanical quality level for commercial briquette production. However, undeniable advantage of investigated materials is the form they occurred in; no further feedstock preparation (drying, crushing) was needed.

Key words: